Method for casting metered quantities of liquid metals

ABSTRACT

An improved method of using travelling field runners in which liquid metal is conveyed therein by travelling magnetic fields to moulds, die casting machines, casting belts and the like by controlling the flow of liquid metal therein from an initially relatively low rate up to a maximum and thereafter continuously reducing the rate from the maximum until a predetermined amount of metal has been poured.

United States Patent 1 1 3,696,858 Seulen et al. 5] Oct. 10, 1-972 METHOD FOR CASTING METERED [5 6] References Cited QUANTITIES OF LIQUID METALS UNlTED STATES PATENTS [721 Invemms Gerhard Seulen Remscheid; Axel 2,753,605 7/1956 Carleton ..164/155 f h 'g 2,970,830 2/1961 Siegfried ..164/133 x rmg ausen, O ermany 2,702,004 2/ 1955 Blake et al ..417/50 [73] Assignee: AEG-Elotherm GmbH, Remscheid- 3,005,116 10/1961 Reece ..417/50 X Hasten, Germany 1 3,534,886 10/1970 VonStarck ..222/1 [22] Filed: May 2, I969 Primary Examiner-Robert D. Baldwm [2]] App! 821342 Attorney-Cushman, Darby & Cushman [30] Foreign Application Priority Data [57] ABSTRACT p 1968 many 17 83 044-3 An improved method of using travelling field runners in which liquid metal is conveyed therein by travelling U.S. CI. magnetic fields to moulds casting machines cast- [51] I t Cl $5133 ing belts and the like by controlling the flow of liquid 1 metal therein from an i i i relatively low rate up to [58] held of Search "164/ a maximum and thereafter continuously reducing the rate from the maximum until a predetermined amount of metal has been poured.

7 Claims, 1 Drawing Figure METHOD FOR CASTING METERED QUANTITIES OF LIQUID METALS This invention relates to the casting of metals from a travelling field runner.

Conveying devices in the form of travelling field runners more commonly called electromagnetic conveyor troughs have recently been proposed in which travelling electromagnetic fields generated by induction windings propel liquid metals up ascending paths contrary to the direction of gravity. Such devices are used for instance for conveying liquid metals, for example for the discharge of vertical furnaces, or they may be used for pouring prescribed quantities of liquid metals into chill moulds, pressure diecasting machines, casting belts and the like. For the latter use voltage is applied to the induction coil of a travelling field runner for the duration of the casting process. Hitherto it has been considered desirable that the rate of flow of metal in the runner is kept constant substantially independently of the liquid level in the furnace vessel.

In practice such travelling field runners have proved to be efficient metering devices. They help to mechanise and automate casting operations and relieve the foundryman of the recurrent task of apportioning an exactly predetermined quantity of liquid metal.

However it has now been discovered that the quality of the casting is considerably improved if the rate of flow of the liquid metal in the runner is variable. Moreover, by pouring metered quantities of the liquid melt into moulds at variable rates of flow, the advantage is gained that the gas in the casting mould can escape unimpeded and that the formation of cavities in the casting is avoided.

The present invention provides a method of casting metered quantities of liquid metals with the aid of a travelling field runner, and consists in starting the metered casting operation at a low pouring rate of the metal, then increasing the pouring rate to a maximum and thereafter continuously reducing the pouring rate until the entire predetermined quantity of liquid metal has been cast. In particular instances, for example when casting pigs, it is even desirable to start pouring the liquid metal at the maximum rate and not to decrease the rate until shortly before the metered quantity has been poured, when the pouring rate is rapidly decreased to zero. This provides the advantage that dribbling of liquid metal from the pouring spout of the runner is completely avoided.

An embodiment of the invention is hereinafter described and illustrated in the accompanying drawing, which is a circuit diagram. Referring to the drawing, a three-phase generator 1 delivers a voltage through a three-phase switch 2 to the primaries 3 of a transformer 4. The primary voltage of the transformer 4 induces corresponding voltages in the transformer secondaries 5 each of which is provided with a tap 6 connected to a tap 7 on the three-phase inductor winding 14 of an electromagnetic travelling field runner. The tap 7 determines the point along the travelling field runner up to which the metal melt is continuously conveyed up the runner when the switch 2 is closed. From the ends 9 of the secondaries of the transformer 4 conductors 10 lead to variable reactance coils 11 and thence to a switch 12 directly associated with a controller 13 which adjusts the variable reactance coils according to a predetermined programme.

The illustrated arrangement functions as follows:

When the switch 2 has been closed, the generator 1 applies voltage through the transformer 4 and the tap 7 to the inductor winding 14 which continuously feeds the metal forwards. When the second switch 12 is also closed the winding 15 of the inductor which is intended to control the pouring operation receives voltage from the ends 9 of the secondaries of the transformer 4 through the variable reactances 11. At the same time the controller 13 begins to function and to adjust the reactance coils 11 according to a predetermined programme during the time the switch 12 is closed. Variation of the reactances of the reactance coils 11 causes the inductor winding to receive a varying voltage in such manner that at the beginning of the pouring operation the rate of supply of the liquid metal is low, then rises to a maximum from which it again decreases continuously to the end of the pouring operation. Instead of variable reactance coils l1, variable impedances, capacitors, controllable transformers or other equivalent devices may likewise be used. Moreover it is not essential in a three-phase travelling field runner to control all of the three variable reactance coils 11. Generally it should be sufficient if only one of the reactors 11 in one of the phases is controlled.

What is claimed is:

1. A method of casting metered quantities of a liquid metal from a travelling field electromagnetic conveyor trough, comprising the steps of controlling the initial pouring rate of liquid metal to the casting mould at a relatively low pouring rate, subsequently increasing the rate to a maximum, and thereafter continuously reducing the pouring rate from said maximum pouring rate until a predetermined quantity of liquid metal has been poured, said pouring rates being controlled by varying the effective intensity of the travelling field.

2. A method as in claim 1 wherein said steps of controlling, increasing and reducing each include the step of variably controlling the voltage supplied from a source to said travelling field electromagnetic conveyor trough.

3. A method as in claim 2 wherein said step of voltage controlling includes the step of varying the reactance of at least a single variable reactance coil connecting said source to said electromagnetic conveyor trough according to a predetermined program.

4. A method as in claim 3 wherein said step of varying includes the steps of varying together the reactances of three variable reactance coils connecting a three phase source to said electromagnetic conveyor trough via a transformer.

5. A method of casting metered quantities of a liquid metal from a travelling field electromagnetic conveyor trough, comprising controlling the pouring rate of liquid metal during the casting operation whereby a maximum pouring rate is provided, and thereafter continuously reducing the pouring rate from said maximum pouring rate until a predetermined quantity of liquid metal has been poured, said pouring rates being controlled by varying the effective intensity of the travelling field.

6. A method according to claim 1, wherein the said maximum rate occurs during the initial pouring of the liquid metal.

7. A method according to claim 1, wherein the said maximum rate occurs subsequent to the initial pouring. 

1. A method of casting metered quantities of a liquid metal from a travelling field electromagnetic conveyor trough, comprising the steps of controlling the initial pouring rate of liquid metal to the casting mould at a relatively low pouring rate, subsequently increasing the rate to a maximum, and thereafter continuously reducing the pouring rate from said maximum pouring rate until a predetermined quantity of liquid metal has been poured, said pouring rates being controlled by varying the effective intensity of the travelling field.
 2. A method as in claim 1 wherein said steps of controlling, increasing and reducing each include the step of variably controlling the voltage supplied from a source to said travelling field electromagnetic conveyor trough.
 3. A method as in claim 2 wherein said step of voltage controlling includes the step of varying the reactance of at least a single variable reactance coil connecting said source to said electromagnetic conveyor trough according to a predetermined program.
 4. A method as in claim 3 wherein said step of varying includes the steps of varying together the reactances of three variable reactance coils connecting a three phase source to said electromagnetic conveyor trough via a transformer.
 5. A method of casting metered quantities of a liquid metal from a travelling field electromagnetic conveyor trough, comprising controlling the pouring rate of liquid metal during the casting operation whereby a maximum pouring rate is provided, and thereafter continuously reducing the pouring rate from said maximum pouring rate until a predetermined quantity of liquid metal has been poured, said pouring rates being controlled by varying the effective intensity of the travelling field.
 6. A method according to claim 1, wherein the said maximum rate occurs during the initial pouring of the liquid metal.
 7. A method according to claim 1, wherein the said maximum rate occurs subsequent to the initial pouring. 